Indium-antimonide (InSb) has been found to be a particularly useful semiconductor material for making photovoltaic detectors in the 3-5 micrometer wavelength portion of the infrared spectrum. The structure usually consists of an n-type material doped with tellurim onto which is diffused cadmium or zinc to form a p-type layer. Due to the difficulty in masking this diffusion the p-type material has been applied to the entire surface of the n-type material and then the portions between diodes are etched away to produce individual mesas. These mesas become troublesome during the subsequent steps of surface passivation and electrode formation due to the difficulty in controlling the film thickness at the edges of the mesa. This process also produces a certain amount of contamination of the n-type material between the diodes which can lend to poor yields or undesireably large spacing of the diodes.